1. Field of the Invention
The invention relates to key mechanisms used in stringed keyboard instruments, primarily but not limited to pianos, and more particularly relates to apparatus for varying the touch or pressure required to strike a note.
2. Description of the Prior Art
The piano key mechanism is one of a grouping of key mechanisms typically numbering 88 used for propelling felt hammers onto strings thereby producing a tones and music. Piano key levers are depressed or struck by the fingers of the pianist and piano hammers are propelled at an amplified rate of speed onto the strings.
In the prior art of piano key mechanism design, the piano key rests on a pivot bearing which is in a fixed position on a balance rail and is held in place by a metal pivot pin inserted in the balance rail. The pivot bearing is typically a disc of felted wool cloth or a half round section of wood covered in wool felt which is also held in place by the pivot pin. On the rearward side of the key there is most often a metal screw with a smooth top that engages the mechanism for propelling the hammer into the string.
The rate of speed amplification between the finger and key moving down and the hammer moving up to the string is greatly influenced by the location of the balance or fulcrum point of the key lever on the pivot bearing. For any given balance point of a key lever, the closer the fulcrum point is to the pianist, the faster the hammer moves in relation to the key movement when the pianist strikes the key, and the more force that is required by the pianist to play the keys. Also because the hammer is moving more quickly, the downward distance that the key has to move in order for the internal workings of the mechanism to complete their function does not have to be as great. Conversely if the balance point of the key lever is designed to be farther away from the pianist, the hammer moves slower in relation to the key movement when the pianist strikes the key, and the less force is required by the pianist to play the keys. Also because the hammer is moving more slowly, the downward distance that the key has to move in order for the internal workings of the mechanism to complete their function has to be greater.
Pianists typically select a particular piano for the quality of touch or the amount of force required to depress the key when playing the piano. Some like a heavy touch, some like a medium touch, and some like a lighter touch. It all depends on the physiology of the pianist and the type of music they are playing. Pianists who require a lighter touch need a different piano from those who require a heavier touch.
The prior art discloses a number of unique systems in which a key lever fulcrum point is moved within a keyboard instrument to effect the playing characteristics of that instrument. U.S. Pat. No. 1,224,994, Anelli, shows an arrangement in which the key levers remain stationary and the entire balance rail assembly, including the pivot pins, and pivot bearings is longitudinally shifted as a unit with respect to the keys.
U.S. Pat. No. 777,133, Oleson, presents an adjustable secondary follow on fulcrum member for organ keys which is not constructed as part of the primary key fulcrum assembly using a balance rail and pivot pins.
U.S. Pat. No. 619,964, Kringle, illustrates a complex system using weights and a moveable fulcrum which is again a secondary rather than a primary device not directly interacting with a key lever.
U.S. Pat. No. 4,308,783, Absmann, provides for two spaced apart longitudinal pivot pin receiving slots in the key lever so that the lever may be disposed over one or the other of the stationary pivot pins on the balance rail.
Other relatively complicated approaches are disclosed in U.S. Pat. No. 4,381,691, Conklin Jr. et al., using springs; Japanese publication JP2005077848 (A), Ishikawa Akira, using weights; and International Publication Number WO00/54248, Snel et al., employing adjustable magnets.
None of the prior art devices known to applicant appear suitable for use in existing instruments. That is, they must be integrated into the initial construction of the instrument and would not be capable of easily, if at all, being retrofitted into instruments that have already been built. Further, there is no structure of any kind in the prior art which could be employed in applicant's manner even in newly constructed instruments.
Additionally, applicant's invention allows for a multiplicity of touch adjustments along all the keys of an entire keyboard as well as the means to vary the settings unequally, that is, to provide for a lighter touch in one group of keys and a heavier touch in another.